The present invention relates to a device and method of detecting abnormality in ejecting die castings from a die, and more particularly, to such device and method of predicting deformation of the die castings, which may be deformed during the ejection thereof from the die.
A plurality of reversibly slidingly movable ejector pins are conventionally provided for separating and ejecting die castings from a die. The ejector pins are reversibly slidably disposed in pin guide though holes formed in the die. One end of each ejector pin of each ejector pin is fixed to an ejector plate. The ejector plate is connected to a well-known hydraulics cylinder, and is returnably slidable therewith. Consequently, when the hydraulics cylinder slides the ejector plate in an ejection direction, the end of each ejector pin not connected to the ejector plate slides into the die cavity and ejects the die castings from the die.
One cause of deformation in die castingss is galling generated during ejection of the die castings. Such galling prevents uniform ejection of the product from the die. Galling during ejection is produced from various sources such as temperature of the molten metal, temperature distribution of the die, surface condition of the die, and coating condition of release agent. Galling tends to repeat once induced, so that deformed products are consecutively produced rather than in isolated cases.
Conventionally, deformations in die castingss are controlled by measuring size of the die castings produced at a predetermined interval to determine whether or not they meet a set of dimensional standards. Further, the degree of galling generated during ejection is conventionally detected by measuring the hydraulics in the hydraulic cylinder which drives the ejector plate.
However, there has been known a problem with controlling deformations by measuring dimensions of die castingss in that when a defective product is discovered, all the products produced since the previous measurement must also be measured, wasting a great deal of time and expense. Because defective die castingss are measured only at a predetermined interval and not discovered during casting, many defective products may be cast before one in a series of defective products is discovered.
Measuring hydraulics in the hydraulics cylinder can reveal the maximum resistance against the ejector plate, but not details of abnormal movements in the ejector plate. Therefore, differentiating between galling produced at different places is impossible and galling related to generation of distortions can not be detected.